TAMPA, Fla.– Over the summer, Bain became a four-letter word for Mitt Romney.

On Thursday at the Republican National Convention, some of Mr. Romney’s closest business associates painted a different portrait of the private-equity firm he founded, Bain Capital.

Mr. Romney’s longtime business partner Bob White and Staples founder Tom Stemberg were brought to the convention podium to push back against Democratic attacks on the private equity firm, calling the criticism “fiction,” “half-truths” and “downright lies.”

Until recently, Mr. Romney had seemed reluctant to push back against his critics, but his campaign is now moving more aggressively – in videos on his campaign website and shown at the convention as well as in the convention speakers – to put luster onto the most intensely criticized part of his business career.

“My life today is better because of Bain Capital,’’ Ray Fernandez, a Cuban immigrant whose contact lens business was turned around by the firm, told the convention. “Mitt Romney helped turn around my company. I can’t imagine anyone better prepared to turn around this country.

Democrats have portrayed his Bain work as greed-driven investments that often cost workers jobs and dismantled companies – a critique that began months ago by fellow Republicans trying to discredit Mr. Romney in the GOP primary. More recently, an ad by Obama supporters spotlighted a steel plant closure drew special controversy because it blamed Romney for the death of the wife of a laid off steelworker.

Mr. Stemberg described how Mr. Romney’s investment had helped him carry out his plan to “do to office supplies what Home Depot had done with home improvement’’ and helped launch Staples, the office supply company that today employs nearly 90,000 people.

“For me, as a founder, it was the realization of a dream,’’ Mr. Stemberg told the convention. ”So you can imagine my dismay, when I see this White House and their campaign demonizing Mitt Romney.’’

“When it comes to jobs, new businesses and economic growth – they just don’t get it,’’ he said.

Mr. Stemberg accused the Obama campaign of “demonizing” private equity. But in defending Mr. Romney, he didn’t actually cite any private equity deals done by Bain. Instead, he elided over the more controversial parts of Mr. Romney’s Bain career by focusing on the same handful of Bain Capital successes often cited by Mr. Romney, such as Staples, day-care provider Bright Horizons, and steel producer Steel Dynamics. All of these were not private-equity deals, but venture capital deals in which Bain was one of a number of investors helping to get a nascent company off the ground. The total Bain invested in those three firms plus Sports Authority, another startup success story often cited by Mr. Romney, was just $25 million, or 2% of the money Bain invested under Mr. Romney.

In other words, Mr. Stemberg was doing just what he accused the Obama campaign of doing – cherry-picking examples from Mr. Romney’s Bain career.

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